PlanetGraham: Mailplane App. The best way to use Gmail on a Mac.

But a few years ago I came across a shareware program called Mailplane that changed everything for me. Mailplane is a small shareware application that gives you all the features of Gmail's web interface via a desktop application. And if you have multiple Gmail accounts, you can manage them all in the same application, without having to sign in and out of your different accounts.